It was all over for SAGE and the radar pickets as well. Able to engage multiple targets a hundred miles away, the new breed of interceptors—McDonnell Douglas’ F-4 and F-15, General Dynamics’ F-16—would also be competent dogfighters and tactical bombers. Where the F-106 had delivered one near-perfect note, the newer aircraft would deliver whole symphonies.

In the end, SAGE, the DEW Line, and the Ultimate Interceptor never had to face the attack they were built to thwart.

Once intercontinental ballistic missiles and “mutual assured destruction” began to dominate strategic thinking, the focus on these specialized interceptors ended. No one can say whether a strong air defense helped deter an attack, or whether such an attack was ever really in the cards.

But even pilots doubt SAGE could have achieved the 70 percent success rate advertised by its founding fathers. “That’s probably optimum,” says Williams. “You’re up there in the furball of war, they’re coming toward you on a one-way mission over the North Pole, sky lit up with nuclear weapons, Nikes going off….”

Many of the old DEW Line sites still stand, ghost towns of abandoned trailers and radomes. Eventually, a U.S. Air Force-funded project called “Cleansweep” will erase their toxic remains from the tundra.

A new radar picket line called the North Warning System, minimally crewed, stretches across the high latitudes.

The face of air defense has changed.The North American Air Defense Command’s fabled Cheyenne Mountain hideaway has shut its bomb-proof doors. In Iceland, American interceptors—not Deuces or F-4s, but F-15 Eagles—are leaving Keflavik. The Air Force has given up Galena.

But interceptor pilots still scramble, now facing the nightmarish possibility of having to chase down a hijacked airliner. The golden age of air defense may be over, but the work continues.